title: Evidence of melatonin synthesis in the cumulus oocyte complexes and its role in enhancing oocyte maturation in vitro in cattle.
abstract: Melatonin is a multifunctional molecule that mediates several circadian and seasonal reproductive processes. The exact role of melatonin in modulating reproduction, however, is not fully understood-especially its effects on the ovarian follicles and oocytes. This study was conducted to investigate the expressions of the ASMT and melatonin-receptor MTNR1A and MTNR1B genes in bovine oocytes and their cumulus cells, as well as the effects of melatonin on oocyte nuclear and cytoplasmic maturation in vitro. Cumulus-oocyte complexes (COCs) from abattoir ovaries were cultured in TCM-199 supplemented with melatonin at concentrations of 0, 10, 50, and 100 ng/ml. The expression of ASMT, MTNR1A, and MTNR1B genes was evaluated by RT-PCR. Moreover, the effects of melatonin on cumulus cell expansion, nuclear maturation, mitochondrial characteristics and COCs steroidogenesis were investigated. Furthermore, the level of reactive oxygen species (ROS) was evaluated in denuded oocytes. Our study revealed that ASMT and MTNR1A genes were expressed in COCs, while the MTNR1B gene was expressed only in oocytes. Additionally, melatonin supplementation at 10 and 50 ng/ml to in vitro maturation medium significantly enhanced oocyte nuclear maturation, cumulus cell expansion and altered the mitochondrial distribution patterns, but had no effects on oocyte mitochondrial activity and COCs steroidogenesis. Melatonin-treated oocytes had a significantly lower level of ROS than controls. The presence of melatonin receptors in COCs and its promoting effects on oocyte nuclear and cytoplasmic events, indicate the potentially important roles of this hormone in regulating bovine oocyte maturation. Moreover, the presence of ASMT transcript in COCs suggests the possible involvement of these cells in melatonin biosynthesis.
authors.affiliation: Reproductive Biology and Technology Research Team, National Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Mohamed
authors.initials: M
authors.lastname: El-Raey
authors.forename: Masaya
authors.initials: M
authors.lastname: Geshi
authors.forename: Tamás
authors.initials: T
authors.lastname: Somfai
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kaneda
authors.forename: Makoto
authors.initials: M
authors.lastname: Hirako
authors.forename: Alaa E
authors.initials: AE
authors.lastname: Abdel-Ghaffar
authors.forename: Gamal A
authors.initials: GA
authors.lastname: Sosa
authors.forename: Mahmoud E A Abou
authors.initials: ME
authors.lastname: El-Roos
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagai
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism; D054885:Cumulus Cells / Q000166:cytology / Q000201:enzymology*; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D008550:Melatonin / Q000096:biosynthesis; D008928:Mitochondria / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D009866:Oogenesis / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D044122:Receptor, Melatonin, MT1 / Q000096:biosynthesis*; D044123:Receptor, Melatonin, MT2 / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017382:Reactive Oxygen Species; D044122:Receptor, Melatonin, MT1; D044123:Receptor, Melatonin, MT2; D000121:Acetylserotonin O-Methyltransferase; D008550:Melatonin